Model Newcomen engine, repaired by James Watt, 2000

Hunterian Museum of the University of Glasgow, Scotland. This model of a Newcomen atmospheric engine was fixed by James Watt, when working as an instrument repairer. As a result of fixing this model, Watt realized that Newcomen engines use steam inefficiently. This led to Watt developing the steam engine, in which expanding steam pushes a piston in a cylinder. In a Newcomen engine, the condensation of steam pulls a piston. In addition, steam is condensed in a Newcomen engine by spraying cold water into the cylinder.